In a communications network, trunks are used as facilities to interconnect different nodes of the network. Occasionally, such a trunk becomes defective but does so in such a way that the defect is not detected by the traditional, operational tests integrated into conventional call processing procedures. For example, in a telephone network, a trunk may appear to be operationally satisfactory to central office equipment but is actually nonusable for communication because it is excessively noisy or speech communication may be impossible over the trunk. When such a trunk is engaged on a call, a customer usually detects the inoperative condition and terminates the call after a very short holding time. Customarily, no trouble or maintenance record is made of such calls and occasionally the telephone company is made aware of the poor service condition only by a customer complaint.
These defective trunks create an especially serious situation during the busy hour. Since such trunks have naturally short holding times, they become repeatedly available for customer use and are responsible for a substantial number of unsuccessful call attempts.
In a toll telephone network, many such trunks are detectable because they are used on operator calls. According to established practices, operators are instructed to key information into the system which provides for a maintenance record of call details including the indentity of the trunk used on the call. That record is subsequently analyzed to identify the trunk. However, for trunks which are not used by operators, automatic detection and identification becomes much more difficult. The problem is particularly acute in private networks, such as Enhanced Private Switched Communications Services which use a relatively small number of trunks. Because of such a deficiency, the customer is often subjected to the seizure and use of the same defective trunk several times before a successful call can be completed.
In view of the foregoing, it is apparent that a need exists for a method of identifying defective trunks having the foregoing problems and for doing so with a minimum of additional overhead call processing.